Replace sizeof("string")-1 with strlen("string") We want to avoid calls to strlen at runtime if the string is already known at compile time. Turns out that gcc and clang will recognize constant strings and compute the strlen result already at compile time, so trickery with sizeof only reduces readability but does not improve the code. Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net> Index: flashrom-const_strlen/processor_enable.c =================================================================== --- flashrom-const_strlen/processor_enable.c (Revision 1183) +++ flashrom-const_strlen/processor_enable.c (Arbeitskopie) @@ -56,13 +56,13 @@ while (*ptr && isspace(*ptr)) ptr++; /* "cpu" part appears only with some Linux versions. */ - if (strncmp(ptr, "cpu", sizeof("cpu") - 1) == 0) - ptr += sizeof("cpu") - 1; + if (strncmp(ptr, "cpu", strlen("cpu")) == 0) + ptr += strlen("cpu"); while (*ptr && isspace(*ptr)) ptr++; - if (strncmp(ptr, "model", sizeof("model") - 1) != 0) + if (strncmp(ptr, "model", strlen("model")) != 0) continue; - ptr += sizeof("model") - 1; + ptr += strlen("model"); while (*ptr && isspace(*ptr)) ptr++; if (*ptr != ':') @@ -72,9 +72,9 @@ ptr++; fclose(cpuinfo); return (strncmp(ptr, "ICT Loongson-2 V0.3", - sizeof("ICT Loongson-2 V0.3") - 1) == 0) + strlen("ICT Loongson-2 V0.3")) == 0) || (strncmp(ptr, "Godson2 V0.3 FPU V0.1", - sizeof("Godson2 V0.3 FPU V0.1") - 1) == 0); + strlen("Godson2 V0.3 FPU V0.1")) == 0); } fclose(cpuinfo); return 0; -- http://www.hailfinger.org/
Don't know whether I can ack this, but after modifiying the conditionals to always compile that part of the code, gcc did in fact compute the strlen result. $ gcc -v Using built-in specs. Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.4.4-14ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5) Relevant outputs from processor_enable.c.003t.original after adding -fdump-tree-original to CFLAGS in the Makefile are inlined: On 30 September 2010 02:41, Carl-Daniel Hailfinger < c-d.hailfinger.devel.2006@gmx.net> wrote:
Replace sizeof("string")-1 with strlen("string")
We want to avoid calls to strlen at runtime if the string is already known at compile time. Turns out that gcc and clang will recognize constant strings and compute the strlen result already at compile time, so trickery with sizeof only reduces readability but does not improve the code.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Index: flashrom-const_strlen/processor_enable.c =================================================================== --- flashrom-const_strlen/processor_enable.c (Revision 1183) +++ flashrom-const_strlen/processor_enable.c (Arbeitskopie) @@ -56,13 +56,13 @@ while (*ptr && isspace(*ptr)) ptr++; /* "cpu" part appears only with some Linux versions. */ - if (strncmp(ptr, "cpu", sizeof("cpu") - 1) == 0) - ptr += sizeof("cpu") - 1; + if (strncmp(ptr, "cpu", strlen("cpu")) == 0) + ptr += strlen("cpu");
if (strncmp ((const char *) ptr, (const char *) "cpu", 3) == 0) { ptr = ptr + 3; }
while (*ptr && isspace(*ptr)) ptr++; - if (strncmp(ptr, "model", sizeof("model") - 1) != 0) + if (strncmp(ptr, "model", strlen("model")) != 0) continue; - ptr += sizeof("model") - 1; + ptr += strlen("model");
if (strncmp ((const char *) ptr, (const char *) "model", 5) != 0) { // predicted unlikely by continue predictor.; goto <D.4030>; } ptr = ptr + 5;
while (*ptr && isspace(*ptr)) ptr++; if (*ptr != ':') @@ -72,9 +72,9 @@ ptr++; fclose(cpuinfo); return (strncmp(ptr, "ICT Loongson-2 V0.3", - sizeof("ICT Loongson-2 V0.3") - 1) == 0) + strlen("ICT Loongson-2 V0.3")) == 0) || (strncmp(ptr, "Godson2 V0.3 FPU V0.1", - sizeof("Godson2 V0.3 FPU V0.1") - 1) == 0); + strlen("Godson2 V0.3 FPU V0.1")) == 0); }
fclose (cpuinfo); return strncmp ((const char *) ptr, (const char *) "ICT Loongson-2 V0.3", 19) == 0 || strncmp ((const char *) ptr, (const char *) "Godson2 V0.3 FPU V0.1", 22) == $ }
fclose(cpuinfo); return 0;
_______________________________________________ flashrom mailing list flashrom@flashrom.org http://www.flashrom.org/mailman/listinfo/flashrom
On 9/29/10 5:41 PM, Carl-Daniel Hailfinger wrote:
Replace sizeof("string")-1 with strlen("string")
We want to avoid calls to strlen at runtime if the string is already known at compile time. Turns out that gcc and clang will recognize constant strings and compute the strlen result already at compile time, so trickery with sizeof only reduces readability but does not improve the code.
Signed-off-by: Carl-Daniel Hailfinger<c-d.hailfinger.devel.2006@gmx.net> Acked-by: Sean Nelson <audiohacked@gmail.com>
Carl-Daniel, please run 'svn up' in the source directory before committing, as the patch won't apply directly as-is. svn will handle the merge correctly. Thanks! On 15 October 2010 01:47, Sean Nelson <audiohacked@gmail.com> wrote:
On 9/29/10 5:41 PM, Carl-Daniel Hailfinger wrote:
Replace sizeof("string")-1 with strlen("string")
We want to avoid calls to strlen at runtime if the string is already known at compile time. Turns out that gcc and clang will recognize constant strings and compute the strlen result already at compile time, so trickery with sizeof only reduces readability but does not improve the code.
Signed-off-by: Carl-Daniel Hailfinger<c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Sean Nelson <audiohacked@gmail.com>
_______________________________________________ flashrom mailing list flashrom@flashrom.org http://www.flashrom.org/mailman/listinfo/flashrom
On Fri, Oct 15, 2010 at 02:06:16PM +0200, David Borg wrote:
Carl-Daniel, please run 'svn up' in the source directory before committing, as the patch won't apply directly as-is. svn will handle the merge correctly. Thanks!
Updated patch attached. It's also Acked-by: Uwe Hermann <uwe@hermann-uwe.de> Uwe. -- http://hermann-uwe.de | http://sigrok.org http://randomprojects.org | http://unmaintained-free-software.org
Am 18.06.2011 23:12 schrieb Uwe Hermann:
On 15 October 2010 01:47, Sean Nelson <audiohacked@gmail.com> wrote:
Acked-by: Sean Nelson <audiohacked@gmail.com> Acked-by: Uwe Hermann <uwe@hermann-uwe.de>
Thanks, committed in r1352. Regards, Carl-Daniel -- http://www.hailfinger.org/
participants (4)
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Carl-Daniel Hailfinger -
David Borg -
Sean Nelson -
Uwe Hermann